Hydrochloric Acid → 8-Fluoro-7-(2-methyl-phenylamino)-quinoxaline-6-carboxylic acid

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Reaction Conditions

Reaction Steps

The compound methyl 4,5-diamino-3-fluoro-2-(2-methyl-phenylamino)-benzoate (from Step e, Example 1) is dissolved in 2:1:1.2 v/v/v of 2.0 M acetic acid-4.0 M sodium acetate-methanol. The suspension is warmed to 65° C. (or until homogeneous) and the clear solution is poured into a 0.078 M aqueous sodium glyoxal bisulfite (Aldrich, monohydrate, 1.05 equiv.) solution which is warmed to 70° C. The reaction mixture is stirred gently between 55-75° C. for one hour, and is then cooled to 12° C. with an ice-water bath. Pulverized sodium hydroxide pellets (27 equiv.) are added to the cold solution. The mixture is gently warmed to 30° C. and stirred for 45 minutes. The temperature is raised to 70° C. for 15 minutes. The mixture is allowed to cool and is treated with ethyl acetate. The biphasic mixture is treated with concentrated aqueous hydrochloric acid to achieve pH 0 in the aqueous phase. The organic phase is separated, dried (MgSO4), and concentrated in vacuo to give the desired product. The product may be triturated with an appropriate solvent like dichloromethane or recrystallized from a solvent like ethanol for further purification as necessary.

Provenance & Evidence